The present invention relates to security in exchanging data via a network, and particularly relates to security in transmitting an original image or processed data of a partial image or the like produced by working the original image when an image obtained by scanning a form, chit, slip or the like is electronically exchanged via a network.
As technology relating to security in data transmission, for example, there has been known a digital signature disclosed, for example, in S. Tujii and M. Kasahara: Cryptography and Information Security, p. 127–139, SHOKODO (1999).